Feeder controls for a forage harvester

ABSTRACT

An agricultural harvesting machine, such as a forage harvester comprises a set of feedrolls ( 20, 21, 26, 27 ) for feeding harvested crop material to a rotating cutterhead ( 36 ). The feedrolls are driven by a hydraulic drive means comprising a hydrostatic pump ( 123 ) coupled to the engine ( 70 ) of the harvesting machine, a hydrostatic motor ( 80 ) coupled to said feeder means ( 20, 21, 26, 27 ) and hydraulic circuitry ( 142, 143, 152 ) interconnecting the pump and the motor. The circuitry comprises a feeder arrest valve ( 165 ) which is operable to interrupt the oil flow from said hydrostatic motor ( 80 ), thereby arresting said feedrolls ( 20, 21, 26, 27 ). The hydrostatic motor ( 80 ) is provided with a flushing valve ( 156 ) for diverting part of the oil flow in said circuitry through said motor for lubricating and cooling the latter. The arrest valve ( 165 ) is provided in said circuitry ( 142, 143, 152 ) between the hydrostatic motor ( 80 ) and the flushing valve ( 156 ). This arrangement allows for an immediate and efficacious arresting of the feedrolls upon detection of a foreign object in the harvested crop.

TECHNICAL FIELD OF THE INVENTION

[0001] The present invention relates to agricultural harvesting machinesprovided with feeder means for feeding harvested crop material to cropprocessing means. More particularly, it relates to feeder means whichare driven by a hydraulic motor and which are provided with means forimmediately arresting said feeder means upon detection of a foreignobject in the crop material.

BACKGROUND ART

[0002] It is well known in the art to provide agricultural harvestingmachines, such as forage harvesters, with an apparatus for detectingforeign material in the stream of crop material which is being fed to acrop processing unit, such as a rotating cutterhead co-operating with astationary shear bar. Such detector apparatus may be a metal detector ofthe type described in EP-B-0,102,665. The signal generated by thisdetector is fed to feeder arrest means, which provoke an immediate stopof the means feeding the crop material to the cutterhead. Thus isprevented that stray metal objects, which were picked up from the field,reach the cutterhead and cause serious damage to the knives and theshear bar. The arrest system also prevent that smaller metal particlesare comminuted by the cutterhead and mixed with the crop which is fed tothe cattle.

[0003] Typical mechanical arrest means as disclosed by U.S. Pat. No.5,921,071 and U.S. Pat. No. 4,296,591 comprise a ratchet wheel which ismounted to the drive line of the feedrolls of the feeder means and apawl which is positioned to engage this ratchet upon detection of metal.The movement of the pawl is controlled by a solenoid which is operatedby the foreign material detector. Actuation of the pawl has to becombined with the simultaneous deactivation of a clutch in the driveline of the feedrolls to prevent damage to the engine or components ofthe drive line.

[0004] The use of such clutch is not required when the feeder means aredriven by a hydrostatic motor as described in EP-A-0,848,902. Thehydraulic circuitry then may be equipped with an arrest valve which isoperable to cut the oil flow to or from the motor upon detection of aforeign object as suggested by FR-A-2,173,352. Such systems may worksatisfactorily when used on the former low capacity forage harvesters.However, it has been experienced that serious problems as to reaction.speed and life time emerged when such systems are applied to thepresent-day high capacity harvesters in which the rotating feedrollshave a greater kinetic energy. Especially the low reaction time iscritical as the foreign object may have the time to reach thecutterhead.

[0005] It therefore is an object of the present invention to provide adrive and arrest system for the feeder means which, on the one hand,does not require a clutch which has to be disengaged upon detection of aforeign object, and, on the other hand, is sufficiently powerful andfast to halt the crop flow before the foreign object reaches the cropprocessing means, even on larger harvesters.

SUMMARY OF THE INVENTION

[0006] According to the present invention there is provided anagricultural harvesting machine, comprising:

[0007] crop processing means operable to process harvested cropmaterial;

[0008] feeder means for feeding said harvested crop material to saidcrop processing means;

[0009] motor means; and

[0010] hydraulic drive means for providing driving power to said feedermeans, said hydraulic drive means comprising a hydrostatic pump coupledto said motor means, a hydrostatic motor coupled to said feeder meansand hydraulic circuitry interconnecting said hydrostatic pump and saidhydrostatic motor;

[0011] said hydraulic circuitry comprising a feeder arrest meansoperable to interrupt the oil flow from or to said hydrostatic motor,thereby arresting said feeder means;

[0012] characterised in that:

[0013] said hydrostatic motor is provided with a flushing means fordiverting part of the oil flow in said circuitry through said motor andto an oil tank or a cooling means; and

[0014] said feeder arrest means is provided in said circuitry betweensaid hydrostatic motor and said flushing means.

[0015] This arrangement does not require any mechanical clutches orpawls to arrest the feeder means. The particular location of the arrestmeans precludes the escape of blocked oil via the flushing circuit, suchthat the motor can be stopped more abruptly and the passage .of foreignobjects into the crop processing means is prevented.

[0016] The flushing means may comprise a flushing valve arranged betweenthe high pressure and the low pressure lines of the motor and the arrestmeans an arrest valve operable to block the high or low pressure line ofthe motor. Advantageously these valves are incorporated into a singlevalve assembly which is mounted to the motor housing. In this manner thevolume of oil between the motor and the arrest valve can be limited,thus improving the reaction speed of the arrest system.

[0017] The hydraulic circuitry may also comprise valve means forhydraulically driving other components in the harvester while the feedermeans are halted. For example the hydrostatic motor may be used fordriving the crop processing means in a reverse sense, opposite to thenormal, crop processing sense. On a forage harvester, this may be usedfor improved sharpening of the cutterhead knives. Also these valves maybe incorporated into the valve assembly.

[0018] Where the arrest system has to assume a high energy load, it maybe advantageous to use an arrest valve which is pilot controlled by asolenoid actuated control valve. To improve the reaction time of suchpilot controlled valve it may be useful to provide the circuitryadjacent the motor with a hydraulic accumulator which is connected viathe solenoid actuated valve to the pilot controlled valve.

[0019] For removing the hydraulic load on the motor after operation ofthe arrest means, the circuitry may comprise by-pass means. Theseby-pass means may be combined with the valves which are used for drivingthe crop processing means in a reverse direction.

[0020] The arrest means may be actuated by a foreign object detector,e.g. a metal detector or an acoustic stone detector, which generates asignal upon detection of a foreign object in the crop flow. The signalis received by a controller comprising signal processing means, whichactuates the arrest means.

DESCRIPTION OF THE FIGURES

[0021] An agricultural harvesting machine -in accordance with thepresent invention will now be described in greater detail, by way ofexample, with reference to the following drawings, in which:

[0022]FIG. 1 is a schematic, side elevational view of a forageharvester, having an engine and a front unit, comprising a feedrollassembly and a cutterhead;

[0023]FIG. 2 is a schematic view of the drive lines and the drivencomponents of the forage harvester of FIG. 1; and

[0024]FIG. 3 is a scheme of a portion of the hydraulic circuitry of aforage harvester according to FIG. 1.

DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

[0025] The terms “front”, “rear”, “forward”, “rearward”, “right” and“left” used throughout this specification are determined with respect tothe normal direction of movement of the machine in operation and are notto be construed as limiting terms.

[0026] In FIG. 1, there is shown a forage harvester having a main frame1 on which there are mounted ground engaging traction wheels 2 andsteering wheels 3. The forage harvester is shown equipped with a cropcollecting apparatus, in the form of a row crop attachment 10, suitablefor the harvesting of maize, but which can be replaced with aconventional windrow pick-up device or a conventional cutter barattachment, depending on the type of crop to be harvested. Customarily,the row crop attachment 10 comprises an attachment frame 12, whichsupports a plurality of row crop units 14, operable to harvest maizestalks from the field and to convey the same rearwards to an auger 16,which in turn delivers the crop material to the bite of feeder meansinstalled in a front unit of the forage harvester.

[0027] Said feeder means comprise lower feeder means, including aforward lower feedroll 26, and a smooth, rear lower feedroll 27, andupper feeder means, including a forward upper feedroll 20 and a rearupper feedroll 21. Said upper and lower feeder means are rotated toconvey the crop material inbetween to a cutterhead 36, which is mountedwithin a cutterhead frame 34 and comprises a plurality of knives 37,generating a cylindrical peripheral shape or profile when the cutterhead36 is rotated.

[0028] During normal harvesting operation, when the cutterhead 36 isrotated about a shaft 39 in its normal operation sense, as indicated byarrow F in FIG. 1, the knives 37 cooperate with a fixed shearbar to cutthe crop material to length and to project it to a pair ofcounter-rotating crop processor rolls 38, which crack the whole kernelswhich are left in the chopped material. The rolls 38 deliver the crop toa blower rotor 49 which is installed within a blower housing 48. Theblower rotor 49 comprises a plurality of paddles 50, which throw thematerial upwardly through the blower outlet into a discharge spout 52,which can be positioned by an operator to direct the cut crop materialas required, normally into a wagon which is moving alongside or behindthe forage harvester.

[0029] Above the cutterhead 36, there may be mounted a knife sharpeningdevice (not shown), comprising a sharpening stone. During sharpeningoperation the stone is moved to-and-fro between the side plates of thecutterhead frame 34, while the stone is gradually lowered towards therotating cutterhead 36. In order to obtain optimum cutting edges for theknives 37, the cutterhead 36 is rotated in a sense opposite to thenormal operation sense, indicated by arrow F.

[0030] As shown in FIG. 1, the forage harvester is driven by a powerplant or engine 70, to which a power-take-off (PTO) gearbox 71 isdrivingly connected. The output shaft 72 of the PTO gearbox 71 is linkedto a universal joint 74 of a drive shaft 73, whereof another universaljoint 74 is linked to a transmission 75. An output shaft of thetransmission 75 is connected to a blower drive shaft 77, which drives ablower gearbox 78 which supports and rotates the blower rotor 49.

[0031] The feeder means are driven by a hydrostatic motor 80 whichdrives a lower feedroll transmission 81 on the left hand side of thefront unit, shown in FIG. 2. This transmission 81 is connected directlyto the lower feedrolls 26, 27 and through a drive shaft 83 to the rearupper feedroll 21. On the right hand side of the front unit, an upperfeedroll transmission 84 drivingly interconnects the upper feedrolls 21,20.

[0032] The cutterhead axle 39 carries at its left hand end the innerring of an overrun clutch 87. The outer ring thereof is mounted to agrooved sheave 88. When the cutterhead 37 is rotated in the senseindicated by arrow F in order to comminute incoming crop material, theclutch 87 engages and the sheave 88 entrains a transmission belt 89.Otherwise, when the rotation of the cutterhead 37 is reversed, as duringa sharpening operation, the clutch 87 disengages and the sheave 88stands still.

[0033] The transmission belt 89 drives a smooth sheave 90 connected tothe lower crop processor roll 38 and a grooved sheave 91 connected tothe upper crop processor roll 38.

[0034] The output shaft 72 of the PTO gearbox 71 carries a grooved PTOsheave 95, to which the universal joint 74 of the drive shaft 73 ismounted. The sheave 95 drives by means of a transmission belt 100 asheave 99 carried by a shaft 98. The transmission belt 100, running overboth sheaves 95, 99, can be tensioned by means of an inner idler roll102, which is rotated in an idler arm assembly 103, which is pivotedabout a journal 104, extending from the PTO gearbox 71. The idler roll102 is loaded by a hydraulic cylinder 106.

[0035] A hydraulic gear motor 110 is coupled to the rear end of theshaft 98. A cutterhead drive shaft 111 is connected by a universal joint74 to the front of the sheave 99. The other end of the drive shaft 111is connected by another universal joint 74 to the input shaft of anangle transmission 112, which drives the cutterhead axle 39.

[0036] The PTO gearbox 71 comprises a PTO input shaft 114, which iscoupled at its rear end to the flywheel 115 of the engine 70 and at itsfront end to a first spur gear 116, meshing with a second spur gear 117.The latter gear 117 drives a third spur gear 118, which receives theinput shaft of a hydraulic pump assembly 119, comprising a first squashplate pump 120, which provides driving power to the traction wheels 2, asecond squash plate pump 123, which provides driving power to the feedermeans, and-gear pumps 121, 122. The PTO input shaft 114 is linked to thePTO output shaft 72 by means of a hydraulically actuated clutch 124.When fluid pressure is applied thereto, the clutch 124 becomes engagedand the output shaft 72 is rotated unitarily with the input shaft 114.

[0037] The feeder means are provided with a foreign object detectorwhich is operable to provide a signal to a controller for arresting thefeeder means upon detection of such object in the crop flow. In thepresent embodiment the detector is a metal detector 125 of the typedescribed in EP-B-0,102,665. The detector 125 is installed inside theforward lower feedroll 26. The controller may comprise a microprocessorwhich is programmed to monitor the metal detector signal and toimmediately generate a feeder arrest command when a metal object isdetected.

[0038] A portion of the hydraulic control system is schematicallyrepresented in FIG. 3. When the engine 70 is running, the hydraulic gearpump 122 draws oil from a shunt tank 127 through an oil filter 128 andfeeds it via a hydraulic feed line 132 to a solenoid operated controlvalve 129 and the hydraulic cylinder 106 of the main belt transmission.One output port of the valve 129 is connected to the hydraulic clutch124, the other is connected to the return line 131, which ends in theshunt tank 127.

[0039] Immediately after the start of the engine 70, the valve 129 isstill in its rest position, as shown in FIG. 3, and the feed line 132 ispressurised, as to extend the cylinder 106. The pressure level islimited by a relief valve 130, which is equally connected to the feedline 132. The position of the valve 129 is controlled by an electricalcircuit (not shown), comprising a programmable control unit, such as amicroprocessor.

[0040] In order to engage the hydraulic clutch 124 and start rotatingthe cutterhead 36, the valve 129 is shifted to the right so that thepressure from the feed line 132 is applied to the piston of the clutch124. Only a small amount of leakage oil drips from the clutch into thePTO gearbox 71, which is also connected to the return line 131. The feedline 132 and the cylinder 106 remain pressurised. Consequently, both theblower rotor 49 and the cutterhead 36 are driven by the engine 70.

[0041] The hydraulic oil from the clutch 124 also serves as a lubricantto the bearings and the gears 116, 117, 118 in the gearbox 71. Therebymost of the oil is mixed with air and divided over the inner surface ofthe gearbox 71, which makes the housing of the latter unsuitable for useas a tank from which the oil may be drawn by the gear pump 122.Therefore the surplus oil is delivered to the shunt tank 127, where itcan settle before it is fed to the gear pump 122.

[0042] When the valve 129 is shifted to the left, the feed line 132 isconnected to the return line 131, so that the pressure in the feed line132 drops and the hydraulic clutch 124 disengages. Simultaneously thehydraulic cylinder 106 retracts under the action of the transmissionbelt 100, so that the cutterhead drive shaft 111 is disconnected fromthe blower gearbox 78. When the control valve 129 is shifted back to theright in order to re-engage the clutch 124, it passes through the middleposition, in which only the cylinder 106 is pressurised. The idler roll102 thus is loaded before the clutch 124 starts to rotate the PTO sheave95. This operating sequence prevents unnecessary slippage of the belt100, so that its lifetime will be extended.

[0043] The engine 70 is equally driving the gear pump 121, which drawshydraulic oil from an oil tank 134 and feeds it via another feed line135 to a plurality of hydraulic actuators such as those controlling theposition of the spout 52 or the level of the attachment 10.

[0044] The hydrostatic pumps 120 and 123, which are equally driven bythe engine 70 are electronically controlled, preferably by the samecontroller that monitors the signal from the metal detector 125. In FIG.3, the pump 123 driving the feeder transmission 81 is shown in somefurther detail, but the pump 120 driving the traction wheels 2. may beof the same squash plate pump type.

[0045] The hydrostatic pump 123 is incorporated in a pump housing 140,represented by phantom lines in FIG. 3. The pump 123 providespressurised oil to the hydrostatic motor 80 through a high pressure line142 and receives return oil through the low pressure line 143. The pumphousing 140 comprises an oil feed pump 141 which constantly feeds oil tothe hydrostatic circuitry. Oil drawn from oil tank 134 is pumped intoone of the lines 143 or 142, whichever has the lowest pressure, via acheck valve 145 or 144. Part of the oil provided by the feed pump 141 isdischarged into the pump housing 140 via a pressure relief valve 148 forlubrication and cooling of the hydrostatic pump 123. The oil is drainedinto the oil tank 134 via a filter and heat exchanger 150.

[0046] The hydrostatic motor 80 on the transmission 81 receives oil fromthe hydrostatic pump 123 through a motor valve assembly 152 which ismounted to the housing 154 of the motor 80. The valve assembly 152comprises flushing means deviating part of the oil flow in order toprovide lubricant and coolant oil to the motor 80. In this embodimentthe flushing means are constituted by a flushing valve 156 having threeports and three positions. The position of the valve is controlled bypilots connected to the high and the low pressure lines 142, 143. Thetwo inlet ports are connected to the same lines and the outlet port isconnected to a flushing line 158 via a spring loaded check valve 157.This valve 157 opens under a pressure lower than the pressure in the lowpressure line. When pressurised oil is fed to the motor 80 through line142, the flushing valve 157 is shifted to the right as seen in FIG. 3,thereby connecting the low pressure line 143 to the flushing line 158.Part of the return oil is deviated via check valve 157 to the motorhousing 154 where it is used to lubricate and cool the motor parts. Theused oil from the motor housing 154 is then fed through a furtherflushing line 160 to the housing 140 of the hydrostatic pump 123, whereit is also used to lubricate to pump parts. From there the flushing oilis finally drained to the tank 134.

[0047] The motor valve assembly 152 also comprises by-pass means fordeviating the oil from the high pressure line 142 to the low pressureline 143. In this embodiment, the oil can be deviated through a pair ofsolenoid operated valves 162, 163 having two ports and two positions.When the solenoids are actuated the valves are moved upwards, as seen inFIG. 3, to shut the connection between the lines 142 and 143 and todirect the oil flow from the high pressure line 142 to the hydrostaticmotor 80. When the electrical current to the solenoids is cut, thevalves 162, 163 return to their rest positions and-oil from line 142passes directly to line 143.

[0048] The low pressure line 143 between the hydrostatic motor 80 andthe flushing valve 156 is provided with an arrest valve 165 which isoperable to interrupt the oil flow from the motor, thereby immediatelyarresting the motor 80 and the feedrolls 20, 21 and 26, 27. The arrestvalve 165 is spring loaded to cut the oil flow but a line pressure lessthen the operating pressure in the low pressure line 143 is alreadyoperable to open the valve against the force of the spring and toconnect the motor 80 to the return line 143. This operating pressurefollows from the opening pressure of the check valve 157 behind theflushing valve 156. The arrest valve 165 may be controlled directly by asolenoid. However, in view of the substantial. oil flow and the highpower requirements involved, it is preferable to use a pilot controlledvalve as shown in FIG. 3.

[0049] Herein the arrest valve 165 is controlled by a solenoid actuatedcontrol valve 166 having two positions and three ports. The controlvalve 166 receives pressurised oil from the oil feed pump 141 via apressure line 167. When the solenoid is not energised, the pilot line ofthe arrest valve 165 is connected to the low pressure flushing line 158,such that the arrest valve remains open. When the control valve 166 isactuated, pressurised oil from the line 167 is fed to the arrest valve165 which shuts the low pressure line 143 and stops the motor 80.

[0050] To improve the reaction time of the arrest valve 165 it isadvantageous to provide a source of pressurised oil, such as anaccumulator 170, adjacent the control valve 166. This accumulator isloaded through the pressure line 167 and the check valve 169. Uponactuation of the control valve 166, oil from the accumulator 170 is fedimmediately to the arrest valve 165.

[0051] The sudden halt of the motor 81 may cause unallowable stress onits components. Therefore it may be necessary to allow a momentaryescape of oil through one or more pressure relief valves 172 whichby-pass the arrest valve 165. These relief valves open only atexceptionally high pressures.

[0052] Inbetween the two by-pass valves 162, 163, there is providedanother hydraulic line 175 which is operable to provide oil to the gearmotor 110 for driving the cutterhead 36 in a reverse sense. A returnline 176 feeds the oil from the motor 110 back to the valve assembly 152where it branches onto the low pressure line 143.

[0053] During normal operation of the harvester, the feedrolls 20, 21,26 and 27 are rotated by the hydrostatic motor 80. The solenoids of thetwo by-pass valves 162, 163 are energised to shut the connection.between the high pressure line 142 and the low pressure line 143 and theoil from the hydrostatic pump 123 is forced through the motor 80. Thecontrol valve 166 is not actuated, such that no pressure is available atthe right hand side of the arrest valve 165, which remains open underthe pressure available in the low pressure line 143. The flushing valve156 is shifted to the right to let a portion of the oil flow as alubricant and coolant to the motor housing 154 via the flushing line158. The rotation speed of the feedrolls is determined by the setting ofthe hydrostatic pump 123, which is controlled by the operator throughthe electronic controller. The speed can be varied to change the averagelength of cut for the harvested crop material.

[0054] When a foreign object is detected by the metal detector 125, thecontroller immediately energises the solenoid of control valve 166.Pressurised oil from the pressure line 167 or the accumulator 170 isprovided to the pilot line of the arrest valve 165 which shifts to theleft, thereby cutting the oil flow from the motor 80 to the low pressureline 143. The hydrostatic motor is arrested immediately, such that theforeign object cannot reach the rotating cutterhead 36. Simultaneouslythe controller de-energises the solenoids of the by-pass valves 162,163, which return to their rest positions shown in FIG. 3. In thismanner the high pressure line 142 is connected to the low pressure line143 such that the oil from the hydrostatic pump 123 can circulatefreely, without undue stress on the pump 123 or the motor 80.

[0055] To clear the foreign object from the feeder means, it is requiredto reverse the feedrolls and discharge the crop material forwardly. Whenthe operator passes on a reversing command to the controller, thehydraulic pump 123 is reversed such that pressurised oil is now fed toline 143. When the reverse oil flow is realised the controllerde-energises the control valve 166, such that arrest valve 165 mightreturn to its open position. The by-pass valves 162 and 163 are actuatedto close the bypass circuit between the lines 143 and 142, such that thepressurised oil is forced in the reversed sense through the hydrostaticmotor 80. Meanwhile the flushing valve 156 is shifted to the left toprovide flushing oil -from the line 142 to the flushing line 158. Thecontroller limits the settings of the hydrostatic pump 123, such thatthe feedrolls 20, 21, 26, 27 are reversed at a slow rate. In this mannerthe crop material is deposited near the entrance of the feeder means,from where the operator can remove the foreign object.

[0056] The motor valve assembly is equally used to reverse thecutterhead 36 during sharpening operations. When the operator gives areversing command to the control unit, the controller first uncouplesthe mechanical driveline to the cutterhead 36 by de-energising thecontrol valve 129 of the clutch 124 as described above. The valve 129returns to its rest position shown in FIG. 3. The speed of thecutterhead is monitored by the controller and when it has fallen below apredetermined threshold, the controller actuates the gear motor 110 onthe cutterhead drive line. To this end the hydrostatic pump 123 isdriven in its normal forward direction. The first by-pass valve 162 isopened, while the second by-pass valve 163 remains closed. The solenoidof control valve 166 is energised to make this valve feed pressurisedoil to the arrest valve 165. In this manner the hydrostatic motor isblocked, while the oil from the high pressure line 142 is directed viathe by-pass valve 162 and the line 175 to the reversing motor 110. Themotor is driven in a sense opposite to the arrow F in FIG. 1. The oilreturns through the line 176 to the motor valve assembly 152 and the lowpressure line 143. The squash plate of the hydrostatic pump 123 is movedby the control unit to rotate the cutterhead 36 at a predeterminedspeed, independent of the setting needed for a wanted length of cut forthe feeder means.

[0057] It will appreciated that thus is provided an effective andversatile means for driving and arresting a feeder means in anagricultural harvesting machine. Although the present invention has beendescribed with reference to a forage harvester and a metal detector,other embodiments can be thought of without departing from the originalidea of the invention. For example the metal detector 125 may bereplaced with another foreign object detector, e.g. an acoustic stonedetector. It is also conceivable to use the hydraulic circuitry to driveother types of feeder means, e.g. a belt conveyor, or to use the arrestmeans to stop only one or two of the feedrolls. The valve assembly mayalso be used to redirect the oil flow not only to the reversal motor ofthe cutterhead, but also to other hydraulic motors or actuators on theharvesting machine itself or on auxiliary devices, e.g. to drive or tomove components on the crop collecting apparatus.

1. An agricultural harvesting machine, comprising: crop processing means(36) operable to process harvested crop material; feeder means (20, 21,26, 27) for feeding said harvested crop material to said crop processingmeans (36); motor means (70); and hydraulic drive means for providingdriving power to said feeder means (20, 21, 26, 27), said hydraulicdrive means comprising a hydrostatic pump (123) coupled to said motormeans, a hydrostatic motor (80) coupled to said feeder means (20, 21,26, 27) and hydraulic circuitry (142, 143, 152) interconnecting saidhydrostatic pump and said hydrostatic motor; said hydraulic circuitry(142, 143, 152) comprising, a feeder arrest means (165) operable tointerrupt the oil flow from or to said hydrostatic motor (80), therebyarresting said feeder means (20, 21, 26, 27); characterised in that:said hydrostatic motor (80) is provided with a flushing means (156) fordiverting part of the oil flow in said circuitry through said motor andto an oil tank (134) or a cooling means (150); and said feeder arrestmeans (165) is provided in said circuitry (142, 143, 152) between saidhydrostatic motor (80) and said flushing means (156).
 2. An agriculturalharvesting machine according to claim 1, characterised in that: saidfeeder arrest means comprises a feeder arrest valve (165)and saidflushing means comprises a flushing valve (156); and said arrest valveand said flushing valve are incorporated into a single valve assembly(152) mounted to said hydrostatic motor (80).
 3. An agriculturalharvesting machine according to claim 1 or 2, characterised in that:said crop processing means (36) are provided with a hydraulic motor(110); and said hydraulic circuitry (142, 143, 152) further comprisesreversal valve means (162, 163) for directing the flow from saidhydrostatic motor (80) to the hydraulic motor (110) of said cropprocessing means (36) in order to drive said processing means in a senseopposite to their normal, crop processing sense (F).
 4. An agriculturalharvesting machine according to any of the preceding claims,characterised in that said feeder arrest means comprise an arrest valve(165) applied to the return line (143) of said hydrostatic motor, saidarrest valve being pilot controlled by a solenoid actuated control valve(166).
 5. An agricultural harvesting machine according to claim 4,characterised in that said circuitry comprises a hydraulic accumulator(170) which is connected through said control valve (166) to said arrestvalve (165).
 6. An agricultural harvesting machine according to any ofthe preceding claims, characterised in that said circuitry (142, 143,152) comprises by-pass means (162, 163) for deriving the oil flow fromsaid hydrostatic pump (123) back to said hydrostatic pump whileby-passing said hydrostatic motor (80).
 7. An agricultural harvestingmachine according to claim 6, characterised in that said by-pass means(162,163) are operable to deviate the oil flow from said hydrostaticpump (123) to a further hydraulic actuator (110).
 8. An agriculturalharvesting machine according to claim 7, when appended to claim 3,characterised in that: said further hydraulic actuator comprises thehydraulic motor (110) of the crop processing means (36); and saidby-pass means (162, 163) comprise said reversal valve means.
 9. Anagricultural harvesting machine according to any of the precedingclaims, characterised in that: said harvesting machine is a forageharvester; and/or said crop processing means comprise a cutterhead (36)for comminuting crop material; and/or said feeder means (20, 21, 26, 27)comprise a set of feedrolls (20, 21, 26, 27).
 10. An agriculturalharvesting machine according to any of the preceding. claims,characterised in that said machine further comprises arrest controlmeans, said control means comprising: a foreign object detector (125)operable to generate a signal upon detection of a foreign object in thematerial flow fed to the processing means; and signal processing meansoperable to actuate said feeder arrest means upon receipt of said signalfrom said foreign object detector (125).